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Fate and form of selenium and microbiology analysis for SRF and GBBR development at Brule Mine in BC

British Columbia Mine Reclamation Symposium; University of British Columbia. Norman B. Keevil Institute of Mining Engineering

Pilot-scale column trials are being used to advance Saturated Rock Fill (SRF) and Gravel Bed Bioreactor (GBBR) water treatment technologies for selenium and nitrate treatment at Conuma Resource’s Brule Mine. The operations and treatment conditions were also optimized and are covered in a separate paper titled ‘Use of Column Trials for SRF and GBBR Development for Selenium and Nitrate Treatment at Brule Mine in BC.’ The mine rock provided by Brule was characterized in detail in the context of biogeochemical treatment. These analyses showed it contains nutrients such as phosphorus and iron that decrease the need for certain reagents. Interestingly, selenium treatment occurred at a rate that was faster than nitrate treatment and independent of reagent dosing. This suggests treatment by coupled biogeochemical reactions, pairing sorption and biological reduction mechanisms. Column-scale trials had effective selenium treatment across all temperatures tested (from 4°C to 22°C). Selenium speciation and genomic microbiology profiling were done on the water during operations and on solids at decommissioning. These analyses provided insights into treatment mechanisms and confirmed that while selenium may be initially removed by sorption, it is then reduced and retained in the waste rock primarily in reduced forms. The trials undertook stress testing, including stopping reagents and exposing the substrate to oxygen. These were done in timelines that could correspond to operational challenges such as a pump malfunction or seasonal fluctuations in water levels. The results from these tests suggest minimal risk of selenium release in these stress conditions. Longer trials, such as an on-site demonstration with more selenium loading, will help better understand long-term stability and associated risks and management. Beneficial microbes, including nitrate-reducing and selenium-reducing bacteria, are naturally present in the Brule mine rock and water. These microbes are crucial for the biological treatment processes, with carbon sources like glycerol significantly enhancing microbial activity. A field-scale pilot trial is recommended to further advance the technology readiness level (TRL). A field-scale GBBR could also provide information to further inform a future SRF trial. This project highlights the potential to co-test SRF and GBBR technologies and the ability to optimize them in site-specific contexts for nitrate and selenium treatment.

Conference Paper

eng

Vancouver : University of British Columbia Library

10.14288/1.0447220

Non UBC

Other

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